The heads of some of the world's biggest oil companies have tried to distance themselves from their British rival BP and its disastrous Gulf of Mexico oil spill at a hearing in Washington.

The oil company executives appeared on Capitol Hill as US officials boosted their estimate of how much oil is spilling into the Gulf of Mexico, from between 20,000 and 40,000 barrels a day to between 35,000 and 60,000 barrels per day.

The executives of ExxonMobil, Chevron, Conoco Phillips and Shell insisted the spill would not have happened on their watch, but were attacked by some politicians for being unprepared for a similar disaster.

And ExxonMobil in particular was ridiculed for including plans to deal with walruses - an animal whose range is confined to the Arctic - in its plans for a Gulf of Mexico oil spill.

ExxonMobil has revealed its emergency response plan includes 40 pages on dealing with the media and only nine on dealing with an oil spill.

The grilling came just hours before president Barack Obama is due to make his first Oval Office address to the nation on the oil spill.

Chevron chief executive John Watson led the offensive against BP.

"I believe the independent investigation will show that this tragedy was indeed preventable," he said.

ExxonMobil chief executive Rex Tillerson said his company would never take risks like BP.

"A number of design standards that I would consider to be industry norm were not followed," he said.

Shell president Marvin Odum joined in bagging BP.

"It's not a well that we would have drilled with that mechanical set up - they're our operational concerns," he said.

Chevron and ExxonMobil's chiefs ganged up in explaining where the problems began.

"The casing design and the mechanical barriers that were put in place appear to be different than what we would use," Chevron chief Mr Watson said.

ExxonMobil chief Mr Tillerson added that there were a lot of clear indications of problems with the well in the lead-up to the final loss of control.

BP's US president, Lamar McKay, was handed the job of trying to defend his company.

"I understand everyone's frustration with how long this is taking, but the spill response has actually been pretty effective in terms of dealing with it on the water," he said.

"It's unfortunate we can't get it stopped at the source right now. We're doing everything we can to do that."

However, Democratic congressmen are not convinced that any of the companies would have done a better job than BP of preventing or responding to the oil spill.

Congressman Ed Markey ridiculed ExxonMobil and the others for having almost identical contingency plans for the Gulf of Mexico.

He says the contingency plans include plans to deal with walruses.

"There aren't any walruses in the Gulf of Mexico and there have not been for 3 million years. How can ExxonMobil have walruses in their response plan for the Gulf of Mexico?" Mr Markey said.

The ExxonMobil chief says the company is embarrassed walruses were included in the plans.

"It's unfortunate that walruses were included and it's an embarrassment that they were included," he said.

Meanwhile, the news for BP just keeps getting worse.

A fire started by lightning striking a ship overnight forced the oil giant to temporarily suspend its efforts to collect the oil gushing from the ruptured well.